1. Field of the Invention
The invention relates to a method and an apparatus for blowing mortar or the like.
For practicing of lining tunnels, levels, slopes and others with mortar or concrete, a method of blowing the material by the feeding medium of the compression air is widely employed. This blowing method is divided into a dry blowing and a wet blowing.
The former comprises dry-mixing materials, such as aggregates, cement and others in a vessel, feeding on the compression air into a hose from a nozzle at a blowing machine, adding water nearly the blowing nozzle at the end of the hose or therearounds and blowing the material onto the object. The latter method comprises mixing aggregate and cement with the water in the vessel to prepare a wet mixture, feeding it into the hose from the machine side nozzle, and jetting it from the blowing nozzle.
Such blowing operation is required to provide high strength of product with little non-uniformity or dispersion, enable to feed the material under the pressure as long as possible or control splashing loss or occurrence of dusts. However, the conventional method could not satisfy all of those requirements.
2. Prior Art
The known dry blowing practice has a merit of making it possible to lengthen the feeding distance, since the dry mixed material is quantitatively jetted from a feed mechanism to the blowing nozzle by the compression air while maintaining the dry condition. However, in this operation water is added to the mixed material just before jetting from the blowing nozzle, and therefore mixing with water is insufficient. For this reason, more water is in general added to result in lowering strength of the lining layer owing to heightening the water-cement ratio and consequently to effect large non-uniformity in each of the lining layers. Further, because of much splashing loss or occurrence of dust, and since the material is jetted as reaction is immature even if accelerating agent were added, the effect by this addition could not be fully displayed and there occurs a problem of air pollution by the poisoneous nature of the accelerating agent.
On the other hand, in aforementioned wet blowing practice, the water is in advance added to the mixture of the aggregate and the cement in the vessel, so that the water-cement ratio is made constant in comparison with the dry blowing practice, and it is possible to provide the lining layer of the satisfactory strength with little splashing loss and occurrence of the dust. However, since the wet material of large specific gravity is fed under pressure, the feeding distance is limited accordingly and the blowing apparatus should be moved nearly to steep working place. Besides, the accelerating agent could not be used in this operation, since solidification progresses by reaction with the water during mixing in the vessel, and the mixture sticks to the interior of the vessel, the machine side nozzle or the hose. Thus, the operation becomes impossible soon. It is difficult to secure a sufficient strength at the beginning for lining on the tunnel arch or rapid slop. In the winter season, the method is disadvantageous since cracks caused by expansion of the water in the earth can not be avoided.